This clip was shot at 1000fps. Sam Stosur’s serve actually has quite a bit in common with her forehand. Watch how she coils her upper body and extends her left arm straight up in the air to hold in the coil – just like she does with her forehand. Then the legs push up and the shoulders rotate – just like in the forehand.
And finally, the butt cap of the racket leads the pull upward followed be a very similar torque applied from wrist, hand, and forearm, generating heavy slice on the ball.
In this serve, Stosur is hitting a slice serve, and one of the misconceptions about a slice serve is that you “carve around” the ball – like peeling around an orange. But here you can see Stosur’s hand and racket actually prontate outward so that the strings face the right side line in the follow through after contact.
The slice comes from the angle of the racket face on contact combined with the twisting motion outward.
Continuing on with the importance of the wrist in modern tennis, take a look at some stills from high speed clips I shot of Grigor Dimitrov. He uses the exact same racket orientation in his serve, forehand, and backhand to add whip like rotation and forward movement of the wrist moments before contact.
Wrist action in modern tennis (Click to Enlarge)
The wrist can produce a burst of racket head speed very, very quickly, and really serves as the end of a whip of energy that starts in the lifting of the legs, the uncoiling of the shoulder, the pull of the arm and lag of the racket, and finally ends in a burst of rotation and forward movement of the wrist. When you lay your wrist backwards, 90 degrees to your forearm, and rotate your forearm backwards a bit, you should feel the tension in the wound up wrist. This tension is released moments before contact as the energy from the entire stroke passes into it.
I drew arrows indicating the direction the butt cap of the racket is facing moments before contact. The butt cap is pointed almost sideways on the backhand, and about 45 degrees away from the ball in the serve and forehand. The racket is at a 90 degree angle to the forearm for all three strokes.
In a burst of rotation and forward motion, the racket will end up close to neutral on contact. Completely in line with the forearm on the serve, and a few degrees backwards on the forehand and backhand.
In this serve clip, notice how the orientation of the butt cap of the racket, with the wrist laid back and rotated backwards (supinated), allows him to create a burst of rapid acceleration of the wrist as it rotates the racket into and even after contact (as the hand continues to rotate the racket outward).